The objective in breeding the present novel variety, assigned the denomination Rishon, was to obtain an early ripening mandarin citrus wherein the fruit has few seeds.
In the spring of 1978 a controlled pollination cross between Temple (Citrus Temple Hort. ex Y. Tanaka) as a seed bearing parent and Michal (a cultivar of Israeli origin believed to be a natural hybrid between two Citrus Reticulata Blanco cultivars) as a pollen parent was made at the Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel. The fruits were collected in November 1978 and seeds of these fruits were extracted and subsequently germinated during January 1979. About 50 seedlings were grown from these germinated seeds. Each seedling was top grafted on a mature Sour Orange rootstock growing in the Agricultural Research Organization experimental grove, Bet Dagan, Israel.
The first fruits were observed in October-November 1985 and observations of the fruits were again made 1986 and 1987. One of the 50 scions was designated 1/37. This scion was observed to be fully ripe in the last week of September or the first week in October, a period which is very early in the Israel growing season. The fruits of this selection were yellow-orange in color when fully ripe.
Budwood was taken from the above mentioned selection 1/37 and top-grafted in the spring of 1986 on two mature Sour Orange and two Troyer rootstocks growing in an experimental grove of the Agricultural Research Organization, Bet Dagan, Israel. These trees were also numbered 1/37. The first crop of these trees was obtained in 1988. The yield of the scions grafted onto Troyer rootstocks was good. The fruit was fully ripe in the first week of October. The color of the fruit when fully ripe was yellow-orange, and the fruit was easy to peel. The fully ripe fruit had a pleasant flavor, and the juice had a sugar concentration of about 11.0% and an acid concentration of about 1.4%.